Spinning cots were at one time conventionally made of leather and cork materials but, in recent years, these materials have gradually been replaced by synthetic rubber compositions.
Much research has been conducted to improve the nature of cots used in industry and many changes have been made in the types of materials used. Nevertheless, certain problems remain to be solved. For example, it is known that soft cots, that is, cots having a Shore A hardness of 65-75, will produce high quality yarn. However, soft cots tend to encourage lapping and they are not particularly durable; thus, they are not entirely satisfactory for textile industry use. Conversely, cots having a higher Shore A rating, for example 80 or more, will show greater durability. Nevertheless, they tend to produce lower quality yarn because there is less control of the individual fibers.